Step 3: Pump and Heat Exchange

Step 4: Sit back and relax!

Enjoy The 107 Degree water with friends! It took about 1 day to raise the temperature from tap temp which was around 40 to 107. The temperature outs...

While enjoy a few drinks at a football tailgate during the Fall of 2008 season I had one of those light bulbs light up over my head! It seems a lot of my ideas show up while consuming beverage.

Some Frat guys at another tailgate had a truck bed full of cold water... They thought they were the smartest guys in the world. So I decided I could out do the Frat guys. Being that I live in Montana and the weather dips well below the 20's in November I had a challenge. I started acquiring parts from all over the place. I got a 150 gallon stock tank from a buddy out in Minnesota when I went to his wedding. It measured 4ft Diameter and 2 Ft deep. It fit about 3 people comfortably and 6 uncomfortably!! We used this small hot tub the first year and upgraded this last season for a 9ft Diameter hot tub! Go big or go home! Enjoy!

Step 1: Find a trailer and Suitable Tank

Living in Montana has its perks. One being friends that have farms and trailers you can borrow for free, and two, local Ranch supply stores that will let you buy and return 1000 gallon stock tanks!

The tank is a cattle stock tank. We had maybe 750 gallons in it. Don't over fill it or else it will overflow everywhere when people get in it. We had to ratchet strap it down with lots of straps. And to prevent to much sloshing during transportation we had to strap a few boards onto the front and back.

Why not up the ante next game season by adding bubbles to that tub? In the same way that bubbles transform Plain Jane white wine into magical champagne, they can turn your tailgate lobster pot into a tingly, roiling cauldron of excitement. For a stock tank as big around as yours you probably need the biggest wet/dry vac you can get and 2 inch hose to run around the wall of the tub and to reach the vac. But hell, you're taking the vac back to Walmart after the game anyway, so who cares what it costs? It would definitely cool your water down at a faster rate than without bubbles, but you can offset this somewhat by placing the vac inside the Burger King crown guy's car with the heat set to full blast. Now you're blowing 95 degree air into the tub instead of 25 degree air.

I have been heating my in-ground pool for over 5 years with a BBQ grill. It was slow so I build a "Cajun conversion" that use two 200,000 BTU Cajun propane burners and now it is much faster. See details www.redneckpoolheater.com

My Cajun conversion is portable and would heat your hot tub in about 2 to 3 hours. Plus you can turn off the flames if you have to maintenance anything and not damage your pipes. It would be a lot safer and easier to work I would think.

You might want to also take a look at all the others that have built pool and hot tub heaters on my "other photos" page.

Very coolalthough it's not a very detailed instructable, it gives a general idea of how to do it. I was thinking of something like that for a while myself. Mine would be stationary though. Since it gets cold here as well, insulation will be important. I also want to be able to either heat it with wood/charcoal or with my military gasoline stove. (It's like a Colemans camping stove, just a lot bigger. It has some 20kW power.)So i could fill some 3 gal of leadfree into the stove tank to preheat. Then while sitting in the tub, enjoy firing it with wood and even grill something on the fire. There is a design on instructables where the coil sits in a converted propane tank.

I was wondering if you could use the cooling loop of an engine; you could drain it down and plumb it straight in and then clean it up with clean water. The engine already has a heat exchanger and pump in it.

A friend made a portable shower to take to a motorcycle meet. (not all bikers are grungy). He made a heat exchanger connected to his truck cooling system. Basically the same as a marine engine heat exchanger, it was a tank that contained copper coils (marine units are all stainless steel). The tank was in the antifreeze engine loop and the coils heated the wash water. Was the only hot water in the area and he made lots of friends...

Someone who makes copper coils for beverage purposes once told me to keep the copper from kinking, you can cork one end and fill the tubing with sand. I would think you could use salt instead, then what didn't flush out would dissolve and keep sand out of the works.

Most in ground or framed hot tubs are made of acrylic.. When made of acrylic the tub has to be kept level and not moved, because it can be misshaped and then crack and come apart. So you have to use a material that will have some movement properties. This idea is great!!!

I would say you should take the advice of the good people of Bowling Green Kentucky who build Corvettes and "Wrap your ass in fiber glass" as the saying goes. Plenty of structural strength if you reinforce it with carbon fiber and metal strips and you can form it any way you like. I would suggest making it sit lower on the bed frame and make the wheel wells seating areas in the tub. It will greatly reduce the ride height and put less stress on your truck to tow it. You have inspired me to build one. I will make an instructable project out of it, too. Thanks.

Yes the Trailer was at it's load limit. Thankfully we only had to travel a couple of blocks to get to the stadium. A one ton truck towed it really slow to the game and we didn't have any problems. Definitely a little scary though!

That would be an easy fix if you have a heater bypass valve that lets you adjust how much water goes thru the heat coils. You just gotta have a temp gauge and be paying a little attention. Basicly the same way the H/C valve works in your shower.